It is well known to use roller bearings in either radial or thrust applications. In radial applications, the rollers are arranged between cylindrical, radially spaced races with the individual roller axes parallel to the axis of the races. In thrust applications, the rollers are arranged between generally flat, axially spaced races with the individual roller axes disposed on radial lines normal to the axis of the races, like spokes of a wheel. Both applications are frequently found. Likewise, in the case of one-way clutches that use rollers, both radial and thrust applications with similarly arranged rollers are known. In the case of roller clutches, however, thrust applications are relatively rare.
An example of a thrust type roller clutch with rollers arranged between generally flat races and the individual roller axes disposed on radial lines normal to the axis of the races may be found in the Johnson U.S. Pat. No. 2,259,473, in FIGS. 20-28. There, the rollers are tapered rollers 95 arranged between races 91 and 92. Just as with a radial one-way clutch, the inside surface of one race 92 further includes a plurality of cam ramp surfaces 94 respective to the rollers 95. The rollers 95 wedge between the cam ramp surfaces 94 and the other race 91 to allow relative race rotation in one direction only. In fact, the embodiment disclosed there is bi-directional, meaning that the ramp surfaces 94 are two sided, or generally V-shaped. Two sets of energizing springs 105 bias either side of the rollers 95 toward either side of the V-shaped cam ramp surfaces 94, depending on which direction a control ring 100 to which the springs 105 are mounted is shifted. Thus, allowed relative race rotation in either direction can be selected, but in each mode, the clutch operates as would a conventional one-way clutch with one cam sided ramp surfaces.
One problem to which the above patent does not speak is the effect of centrifugal force on the rollers. In order to operate quickly and efficiently, the energizing springs in a one-way roller clutch should maintain the individual rollers in a ready position in which the side of each roller is lightly engaged with, or at least proximate to and parallel to, its respective cam ramp surface. This assures that each roller will be ready to quickly wedge between its cam ramp surface and the other race to prevent relative race rotation when the races attempt to reverse their relative direction. The effect of the centrifugal force of rotation of the race that carries the cam ramp surfaces and the rollers has the potential to cause the rollers to move out of ready position. The effect of centrifugal force is a potential problem for both radial and thrust type one-way roller clutches, limiting the speeds at which they may operate. In the case of conventional radial one-way roller clutches, the problem is known as roller drift. This refers to the tendency of the centrifugal force of rotation of the radially outer race to throw the rollers radially outwardly, which compresses the energizing spring and moves the roller up the cam ramp surface and out of ready position. The copending U.S. patent application Ser. No. 521,676, which has the same inventor and assignee as the present invention, solves that problem in its own unique way for a radial one-way roller clutch.
In the case of a thrust type one-way roller clutch, a similar problem is presented. The rollers, in the known arrangement, are disposed with their individual axes lying on radial lines normal to the axis of the races, and are biased by energizing springs toward the cam ramp surfaces. The centrifugal force of rotation of the race with the cam ramp surfaces, which also carries the rollers, will cause the rollers to clockwise or counter-clockwise direction, one of which move either away from their respective cam ramp surfaces, out of ready position, or toward their cam ramp surfaces, since the rollers will, in reality, never lie exactly on radial lines. The ready position of the rollers will not be stable with that roller arrangement.